The present invention relates generally to the field of carbonation processes; more specifically, the present invention relates to the use of ammonia in a carbonation process to obtain sodium bicarbonate (NaHCO.sub.3) and/or sodium carbonate (Na.sub.2 CO.sub.3) from natural soda deposits.
The Solvay process is a well-known and efficient process for the production of sodium bicarbonate from sodium chloride (NaCl). However, economical operation of this process requires recycling of ammonia gas (NH.sub.3). This recycling is accomplished through the addition of calcium hydroxide Ca(OH).sub.2, resulting in the formation of calcium chloride (CaCl.sub.2). There are no known cost-effective methods for the environmentally safe disposal of this calcium chloride. Thus, in most parts of the world, including the United States, the storage and disposal of calcium chloride is regulated, thereby curtailing the use of the Solvay process in countries having natural soda deposits.
Accordingly, in the United States and other countries that have soda deposits, sodium bicarbonate is produced from natural soda deposits. These deposits are wide-spread throughout the southwestern United States, in Mexico and in other parts of the world and consist of a mixture of sodium chloride, sodium carbonate, sodium bicarbonate, sodium sulfate, along with other soluble salts. However, in some parts of the world, including the United States, deposits containing solid trona are found. Trona is sodium sesquicarbonate (Na.sub.2 CO3.NaHCO.sub.3.2H.sub.2 O). Trona deposits are often found substantially free of other soluble salts.
The technique generally used for the production of sodium bicarbonate from natural soda deposits is to bubble carbon dioxide gas through the soda brine solution. The introduction of carbon dioxide gas to a solution is known as carbonation.